A metal-oxide semiconductor field effect transistor (MOSFET) has a gate electrode, a substrate, and a gate dielectric layer between the gate electrode and the substrate. By controlling a voltage level at the gate electrode, a conductive channel, in the substrate underneath the gate dielectric layer, is generated or modulated accordingly. In some applications, a gate-to-source breakdown voltage of a MOSFET is increased by increasing a thickness of the gate dielectric layer. In some applications, a drain-to-source breakdown voltage of a MOSFET is increased by introducing a diffused drain region. Various types of MOSFETs are configured to have increased breakdown voltage, including, for example, lateral diffused metal-oxide semiconductor (LDMOS) transistors and double diffused drain metal-oxide semiconductor (DDDMOS) transistors.